Thermostat randomly switches to cool and turns on the AC in the winter

[Flowd23]

Does this mean it is time to replace the thermostat after only 6 years?

[GabrielaG]

Hi Flowd23,

Thanks for reaching out to the community. I'm sorry to hear that your Nest Thermostat is not working as expected and switches to cool randomly on your AC. I'm happy to assist you right now.

To get a better understanding of the situation, please help me out by answering the following questions:

• What type of Nest thermostat do you have?
• When did the issue start?
• Do you see error codes on the screen of the thermostat?
• Does the issue happen on heating only, cooling only, or both?
• Can you please send me a picture of the thermostat wiring?

Any additional details you can provide will be helpful.

Regards,

Gabriela

[Flowd23]

I tried to respond via email.  Should I place the response here?

[GabrielaG]

Hi Flowd23,

I appreciate your response. Yes, the response must be shared with the community in order to continue assisting you with your thermostat. I'll be happy to help you further as soon as I have your response.

Feel free to keep us posted if you have more questions.

Regards,

Gabriela

[Flowd23]

Hi Gabriela:

I have a Nest Learning Thermostat (3rd gen).

I started receiving safety notifications maybe a few weeks or month or so ago,  but was not aware that it was turning on the AC until last week.  

The app would turn blue rather than orange.  I have not noticed any errors on the display.

It happens while the heat is on.  I am in Chicago and it is cold so we won’t need the AC for a while. I also realized it happened around the same time (10:58am).  The last time it happened, I turned the unit off and then turned it back on a few minutes later.  I have not noticed it switching to cool in the last couple of days since then.

I have two Nest thermostats and have not had a problem with the second one.

Debra

[Flowd23]

 

[GabrielaG]

Hi Flowd23,

Thank you so much for keeping me updated. I appreciate the time you have taken to answer my questions. I'm happy to continue assisting you right now.

We need to isolate the issue to identify if the issue is with the backplate of your Nest Thermostat; for this I recommend the steps below:

• Check the power readouts in Technical Info
• Battery
• Voc
• Vin
• Lin
• Swap the other Nest Learning Thermostat display.
• Check if this thermostat has the same problem, switch to cool, and turn on the AC.

If the issue continues, please continue to this step.

• Turn off the power to the HVAC system.
• Swap the W1 wire to the Y1 terminal.
• Turn the power back on at the breaker box.
• Switch to cool mode but expect heat.

Check if the system runs. Some systems take time to start up so allow 5 minutes for the heat to turn on.

Let me know how it goes.

Regards,

Gabriela